The present invention relates to electronic circuits, and more particularly, to techniques for adjusting a phase of a signal.
FIG. 1 illustrates an example of a prior art dynamic phase alignment (DPA) circuit 100. DPA circuit 100 includes clock selection multiplexer circuit 101A, clock buffer circuit 101B, phase detector circuits 102A, counter circuits 102B, and DPA control logic circuit 103.
Circuit 100 receives 8 periodic clock signals PH[7:0] from a phase-locked loop (PLL) circuit. The 8 clock signals PH[7:0] have relative phase offsets of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°. DPA circuit 100 also receives a data signal. DPA circuit 100 selects one of the 8 clock signals PH[7:0] that is nearest to the center of the data sampling window of the data signal. The selected clock signal is used to sample the data signal.
Clock selection multiplexer circuit 101A selects one of the clock signals PH[7:0] as the selected clock signal SCS. Clock buffer circuit 101B buffers the selected clock signal SCS to generate a buffered clock signal. The buffered clock signal is transmitted to inputs of phase detectors 102A. Phase detectors 102A compare the phase of the buffered clock signal to the data signal to generate UP and DOWN output signals. The phase detectors 102A cause the UP signal to be in a logic high state if the data signal toggles while the buffered clock signal is in a logic low state. The phase detectors 102A cause the DOWN signal to be in a logic high state if the data signal toggles while the buffered clock signal is in a logic high state. Counter circuits 102B count up if the UP signal is pulsing high. Counter circuits 102B count down if the DOWN signal is pulsing high.
DPA control logic circuit 103 generates select signals based on the output signals of counter circuits 102B. The select signals are transmitted to select inputs of clock selection multiplexer circuit 101A. DPA control logic 103 adjusts the select signals to cause clock selection multiplexer 101A to change the phase of the selected clock signal SCS based on changes in the output signals of counter circuits 102B.